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Title: Error field impact on mode locking and divertor heat flux in NSTX-U

Abstract

During the 2016 NSTX-U experimental campaign, locked modes in the plasma edge presented clear evidence of the presence of error fields. Extensive metrology and plasma response modeling with IPEC and M3D-C1 have been conducted to understand the various sources of error fields in NSTX-U as built in 2016, and to determine which of these sources have the greatest effect on the plasma. In particular, modeling finds that the error field from misalignment of the toroidal field (TF) coils may have a significant effect on the plasma. Here, the response to the TF error field is shown to depend on the presence of a q = 1 surface, in qualitative agreement with experimental observations. It is found that certain characteristics of the TF error field present new challenges for error field correction. Specifically, the error field spectrum differs significantly from that of coils on the low-field side (such as the NSTX-U error field correction coils), and does not resonate strongly with the dominant kink mode, thus potentially requiring a multi-mode correction. Furthermore, to mitigate heat fluxes using poloidal flux expansion, the pitch angle at the divertor plates must be small (~1°). It is shown that uncorrected error fields may result inmore » potentially significant local perturbation to the pitch angle. Estimates for coil alignment tolerances in NSTX-U are derived based on consideration of both heat flux and core resonant fields independently.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [4]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)(SC-24); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1532736
Alternate Identifier(s):
OSTI ID: 1529148
Report Number(s):
SAND-2019-2558J
Journal ID: ISSN 0029-5515
Grant/Contract Number:  
AC02-09CH11466; FC02-04ER54698; SC0012706; AC05-00OR22725; AC04-94AL85000
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamaks; error fields; NSTX-U

Citation Formats

Ferraro, N. M., Park, J. -K., Myers, C. E., Brooks, A., Gerhardt, S. P., Menard, J. E., Munaretto, S., and Reinke, M. L. Error field impact on mode locking and divertor heat flux in NSTX-U. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab22c4.
Ferraro, N. M., Park, J. -K., Myers, C. E., Brooks, A., Gerhardt, S. P., Menard, J. E., Munaretto, S., & Reinke, M. L. Error field impact on mode locking and divertor heat flux in NSTX-U. United States. doi:10.1088/1741-4326/ab22c4.
Ferraro, N. M., Park, J. -K., Myers, C. E., Brooks, A., Gerhardt, S. P., Menard, J. E., Munaretto, S., and Reinke, M. L. Wed . "Error field impact on mode locking and divertor heat flux in NSTX-U". United States. doi:10.1088/1741-4326/ab22c4. https://www.osti.gov/servlets/purl/1532736.
@article{osti_1532736,
title = {Error field impact on mode locking and divertor heat flux in NSTX-U},
author = {Ferraro, N. M. and Park, J. -K. and Myers, C. E. and Brooks, A. and Gerhardt, S. P. and Menard, J. E. and Munaretto, S. and Reinke, M. L.},
abstractNote = {During the 2016 NSTX-U experimental campaign, locked modes in the plasma edge presented clear evidence of the presence of error fields. Extensive metrology and plasma response modeling with IPEC and M3D-C1 have been conducted to understand the various sources of error fields in NSTX-U as built in 2016, and to determine which of these sources have the greatest effect on the plasma. In particular, modeling finds that the error field from misalignment of the toroidal field (TF) coils may have a significant effect on the plasma. Here, the response to the TF error field is shown to depend on the presence of a q = 1 surface, in qualitative agreement with experimental observations. It is found that certain characteristics of the TF error field present new challenges for error field correction. Specifically, the error field spectrum differs significantly from that of coils on the low-field side (such as the NSTX-U error field correction coils), and does not resonate strongly with the dominant kink mode, thus potentially requiring a multi-mode correction. Furthermore, to mitigate heat fluxes using poloidal flux expansion, the pitch angle at the divertor plates must be small (~1°). It is shown that uncorrected error fields may result in potentially significant local perturbation to the pitch angle. Estimates for coil alignment tolerances in NSTX-U are derived based on consideration of both heat flux and core resonant fields independently.},
doi = {10.1088/1741-4326/ab22c4},
journal = {Nuclear Fusion},
number = 8,
volume = 59,
place = {United States},
year = {2019},
month = {6}
}

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Works referenced in this record:

Mode locking in tokamaks
journal, December 1990


Interaction of tearing modes with external structures in cylindrical geometry (plasma)
journal, July 1993


Neoclassical toroidal viscosity and error-field penetration in tokamaks
journal, May 2008

  • Cole, A. J.; Hegna, C. C.; Callen, J. D.
  • Physics of Plasmas, Vol. 15, Issue 5
  • DOI: 10.1063/1.2838241

Effect of resonant magnetic perturbations on COMPASS-C tokamak discharges
journal, December 1992


Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary
journal, June 2004


Active Control of Type-I Edge-Localized Modes with n = 1 Perturbation Fields in the JET Tokamak
journal, June 2007


Resonant magnetic perturbation experiments on MAST using external and internal coils for ELM control
journal, February 2010


Nonaxisymmetric field effects on Alcator C-Mod
journal, May 2005

  • Wolfe, S. M.; Hutchinson, I. H.; Granetz, R. S.
  • Physics of Plasmas, Vol. 12, Issue 5
  • DOI: 10.1063/1.1883665

Error field experiments in JET
journal, April 2000


 -Limiting MHD instabilities in improved-performance NSTX spherical torus plasmas
journal, April 2003


The spectral basis of optimal error field correction on DIII-D
journal, April 2014


Overview of NSTX Upgrade initial results and modelling highlights
journal, June 2017

  • Menard, J. E.; Allain, J. P.; Battaglia, D. J.
  • Nuclear Fusion, Vol. 57, Issue 10, Article No. 102006
  • DOI: 10.1088/1741-4326/aa600a

Scenario development during commissioning operations on the National Spherical Torus Experiment Upgrade
journal, February 2018


Overview of the physics and engineering design of NSTX upgrade
journal, July 2012


A method to measure poloidal field coil irregularities in toroidal plasma devices
journal, September 1991

  • La Haye, R. J.; Scoville, J. T.
  • Review of Scientific Instruments, Vol. 62, Issue 9
  • DOI: 10.1063/1.1142330

Error field mode studies on JET, COMPASS-D and DIII-D, and implications for ITER
journal, November 1999


Computation of three-dimensional tokamak and spherical torus equilibria
journal, May 2007

  • Park, Jong-kyu; Boozer, Allen H.; Glasser, Alan H.
  • Physics of Plasmas, Vol. 14, Issue 5
  • DOI: 10.1063/1.2732170

Study of in-vessel nonaxisymmetric ELM suppression coil concepts for ITER
journal, January 2008


Spectral asymmetry due to magnetic coordinates
journal, June 2008

  • Park, Jong-kyu; Boozer, Allen H.; Menard, Jonathan E.
  • Physics of Plasmas, Vol. 15, Issue 6
  • DOI: 10.1063/1.2932110

Error Field Amplification and Rotation Damping in Tokamak Plasmas
journal, May 2001


Calculations of two-fluid linear response to non-axisymmetric fields in tokamaks
journal, May 2012


Multi-mode error field correction on the DIII-D tokamak
journal, March 2003


Self-consistent perturbed equilibrium with neoclassical toroidal torque in tokamaks
journal, March 2017

  • Park, Jong-Kyu; Logan, Nikolas C.
  • Physics of Plasmas, Vol. 24, Issue 3
  • DOI: 10.1063/1.4977898

Modeling of active control of external magnetohydrodynamic instabilities
journal, May 2001

  • Bialek, James; Boozer, Allen H.; Mauel, M. E.
  • Physics of Plasmas, Vol. 8, Issue 5
  • DOI: 10.1063/1.1362532

Investigation of resistive wall mode stabilization physics in high-beta plasmas using applied non-axisymmetric fields in NSTX
journal, August 2007


    Works referencing / citing this record:

    A method to measure poloidal field coil irregularities in toroidal plasma devices
    journal, September 1991

    • La Haye, R. J.; Scoville, J. T.
    • Review of Scientific Instruments, Vol. 62, Issue 9
    • DOI: 10.1063/1.1142330

    Modeling of active control of external magnetohydrodynamic instabilities
    journal, May 2001

    • Bialek, James; Boozer, Allen H.; Mauel, M. E.
    • Physics of Plasmas, Vol. 8, Issue 5
    • DOI: 10.1063/1.1362532

    Nonaxisymmetric field effects on Alcator C-Mod
    journal, May 2005

    • Wolfe, S. M.; Hutchinson, I. H.; Granetz, R. S.
    • Physics of Plasmas, Vol. 12, Issue 5
    • DOI: 10.1063/1.1883665

    Computation of three-dimensional tokamak and spherical torus equilibria
    journal, May 2007

    • Park, Jong-kyu; Boozer, Allen H.; Glasser, Alan H.
    • Physics of Plasmas, Vol. 14, Issue 5
    • DOI: 10.1063/1.2732170

    Neoclassical toroidal viscosity and error-field penetration in tokamaks
    journal, May 2008

    • Cole, A. J.; Hegna, C. C.; Callen, J. D.
    • Physics of Plasmas, Vol. 15, Issue 5
    • DOI: 10.1063/1.2838241

    Spectral asymmetry due to magnetic coordinates
    journal, June 2008

    • Park, Jong-kyu; Boozer, Allen H.; Menard, Jonathan E.
    • Physics of Plasmas, Vol. 15, Issue 6
    • DOI: 10.1063/1.2932110

    Calculations of two-fluid linear response to non-axisymmetric fields in tokamaks
    journal, May 2012


    Self-consistent perturbed equilibrium with neoclassical toroidal torque in tokamaks
    journal, March 2017

    • Park, Jong-Kyu; Logan, Nikolas C.
    • Physics of Plasmas, Vol. 24, Issue 3
    • DOI: 10.1063/1.4977898

    Mode locking in tokamaks
    journal, December 1990


    Effect of resonant magnetic perturbations on COMPASS-C tokamak discharges
    journal, December 1992


    Interaction of tearing modes with external structures in cylindrical geometry (plasma)
    journal, July 1993


    Error field mode studies on JET, COMPASS-D and DIII-D, and implications for ITER
    journal, November 1999


    Error field experiments in JET
    journal, April 2000


    Multi-mode error field correction on the DIII-D tokamak
    journal, March 2003


     -Limiting MHD instabilities in improved-performance NSTX spherical torus plasmas
    journal, April 2003


    Investigation of resistive wall mode stabilization physics in high-beta plasmas using applied non-axisymmetric fields in NSTX
    journal, August 2007


    Study of in-vessel nonaxisymmetric ELM suppression coil concepts for ITER
    journal, January 2008


    Resonant magnetic perturbation experiments on MAST using external and internal coils for ELM control
    journal, February 2010


    Overview of the physics and engineering design of NSTX upgrade
    journal, July 2012


    The spectral basis of optimal error field correction on DIII-D
    journal, April 2014


    Overview of NSTX Upgrade initial results and modelling highlights
    journal, June 2017

    • Menard, J. E.; Allain, J. P.; Battaglia, D. J.
    • Nuclear Fusion, Vol. 57, Issue 10, Article No. 102006
    • DOI: 10.1088/1741-4326/aa600a

    Scenario development during commissioning operations on the National Spherical Torus Experiment Upgrade
    journal, February 2018


    Error Field Amplification and Rotation Damping in Tokamak Plasmas
    journal, May 2001


    Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary
    journal, June 2004


    Active Control of Type-I Edge-Localized Modes with n = 1 Perturbation Fields in the JET Tokamak
    journal, June 2007